[quote author=“Scientific American”]The Roots Of Punishment
A finding from a theoretical model of cooperative activity reveals that making an enterprise optional also makes it more sustainable.By Nikhil Swaminathan

Christoph Hauert of Harvard University is into punishment. Not the giving or receiving of it, that is, but in his professional capacity as a researcher into evolutionary dynamics. The question, for him, is how such a behaviour could ever evolve?

Humanity is a gregarious species, we naturally form groups, live together and on the whole co-operate well with each other. But, if most of the benefits of co-operation can be achieved without actually co-operating, how could such semi-altruism be stable? How is it that ‘cheats never prosper’?

Hauert and co-author Karl Sigmund developed a simple mathematical model to investigate this, and discovered a startling result.

When their model contained just three types of behaviour - called cooperators, defectors and punishers - their model was not stable! Even with punishers present to reduce the benefits to defectors (at a cost to themselves), it was the defector behaviour which came to dominate. It was, in effect, the better individual option (although undoubtedly the group fitness would suffer).

However, this effect went away with the introduction of a forth type of behaviour, the non-participant, who neither takes on the risks or costs of a cooperator, nor receives the benefit of a cooperator or defector. In this model, it was the punishers who came to dominate.